Connecting an Arduino to a car’s OBD2 port for data logging or control presents a power challenge. While pin 16 provides constant 12V battery power, it lacks an ignition-switched source, potentially draining the battery. This article explores solutions for obtaining reliable Obd2 Ignition Power for your Arduino project.
The OBD2 port offers convenient access to vehicle data through the CAN bus, but its constant 12V power source (pin 16) poses a problem for continuous projects. Drawing power even when the engine is off can lead to a dead battery. A simple voltage regulator like the MC7805 converts the 12V to 5V for the Arduino, but this results in constant current draw. While devices like the Conecta BlackVue Parking Mode Hardwire Kit offer low-voltage cutoff for dashcams, a dedicated solution for OBD2 ignition power is needed for Arduino projects.
Utilizing a Voltage Regulator with Low Quiescent Current
One solution involves using a voltage regulator with a very low quiescent current. Quiescent current refers to the current consumed by the regulator even when no load is applied. Choosing a regulator with a quiescent current in the microampere range minimizes battery drain when the engine is off. Examples include low-dropout (LDO) regulators specifically designed for battery-powered applications. However, this approach doesn’t completely eliminate current draw.
Implementing a Low-Voltage Cutoff Circuit
A more robust solution incorporates a low-voltage cutoff circuit. This circuit monitors the battery voltage and disconnects the Arduino when the voltage drops below a predetermined threshold, typically around 12V. This prevents the Arduino from draining the battery below a safe starting level. This can be achieved using a voltage comparator and a MOSFET transistor. The comparator compares the battery voltage to a reference voltage, and when the battery voltage falls below the threshold, the comparator switches off the MOSFET, cutting power to the Arduino.
Combining Low Quiescent Current and Low-Voltage Cutoff
Ideally, combine both approaches. Utilize a low-quiescent current regulator to minimize drain during operation and integrate a low-voltage cutoff circuit for complete power disconnection when the engine is off. This ensures minimal battery drain while providing reliable power when the engine is running. This setup involves a voltage regulator, a voltage comparator, a MOSFET, and a reference voltage source.
Leveraging an Ignition-Switched Source from the OBD2 Port
Certain vehicles offer an ignition-switched power source within the OBD2 port itself. Consult your vehicle’s wiring diagram to identify if such a pin exists. If available, this provides a direct and reliable solution for powering your Arduino only when the ignition is on. This eliminates the need for additional circuitry and simplifies the project. However, the availability of this feature varies significantly between car makes and models.
Conclusion
Powering an Arduino project through the OBD2 port requires careful consideration to avoid battery drain. While no single universal solution exists for all vehicles, implementing a low-quiescent current regulator with a low-voltage cutoff circuit offers a reliable approach. Alternatively, identifying an ignition-switched pin within your vehicle’s OBD2 port provides a more direct solution. Remember to consult your vehicle’s wiring diagram and choose components that meet your project’s specific requirements. Always prioritize safety and ensure proper circuit design to avoid damaging your vehicle’s electrical system.
